“IT HAS LONG BEEN RECOGNIZED that the vital capacity (VC) becomes impaired as the lungs become engorged and turgid with blood consequent to a failing left ventricle, but most consider this decrease a late finding representing a manifestation of overt congestive failure. Measurement of VC has been recommended as a clinically useful tool for evaluating response to treatment in patients under medical management for congestive failure.”
http://circ.ahajournals.org/